1. Field of the Invention
The present invention relates to an air massaging device with a precise pressure control.
2. Description of the Prior Art
An air massage device ordinarily has at least one inflatable air bag to massage each arm or leg of the human body. Each air bag is wrapped around as shown in FIGS. 1 and 2, is inflated by pressurized air provided from an air pump, and then is deflated by discharging the pressurized air to the atmosphere. Therefore, each arm or leg is massaged by alternating an inflating time period and a deflating time period of the air bag. It is preferable that each of the air bags has a pressure sensor to monitor a pressure level of the respective air bag. However, as a pressure sensor for every air bag is required for an air massage device having a plurality of the air bags, such an air massage device creates difficulties because of necessary complex circuits and its expensive cost. This was a first problem in the prior art.
If a pressure level of each air bag is able to be monitored by a single pressure sensor, i.e., the pressure sensor arranged on the side close to the air pump, not in the air bag, this first problem of the prior art can be improved. However, a second problem will then occur. That is, a difference between a practical pressure level of the air bag and a pressure level monitored by the sensor is caused by a flow resistance of a hose tube connecting between the air pump and the air bag. The flow resistance increases as a bore of the hose tube is smaller and as an exhaust capability of the air pump is higher.
It was proposed that the monitored pressure level is corrected by defining a correlation of the monitored pressure level to the practical pressure level of the air bag, so that the second problem will be improved. However, the corrected value is influenced by different sizes of arms or legs of the human bodies wrapped by the air bag.
It was also proposed that the pressurized air provided from the air pump is fed to the air bag for a predetermined time period. However, once again, the monitored pressure level is changed by different sizes of the arms or legs. That is, when a thick arm or leg is massaged, the monitored pressure level is higher; on the other hand, when a thin arm or leg is massaged, the monitored pressure level is lower.